1. Field of the Invention
This invention relates to a vibration wave driven apparatus in which a resilient member in which a travelling vibration wave is formed is of a closed loop shape having at least straight portions, for example, an elliptical shape.
2. Related Background Art
A vibration wave driven motor in which an AC voltage is applied to an electro-mechanical energy conversion element such as a piezo-electric element in a vibration member having the electro-mechanical energy conversion element secured to a ring-shaped metallic resilient member to thereby excite a travelling vibration wave in the resilient member and create elliptical movement of surface particles and thereby rotatively move a member which is in pressure contact with the resilient member has already been put into practically used. Also, in a vibration wave driven motor for rectilinear driving wherein a vibration is caused from one end of a straight beam-like resilient member and is absorbed by the other end of the resilient member to there create a travelling vibration wave for rectilinear driving or a vibration wave driven motor using a vibration member of a closed loop shape, there has been proposed a method of utilizing the tangential force of said ring-shaped vibration member or a method of bringing a contact member into contact with the straight portions of a resilient member having arcuate portions and straight portions to thereby create rectilinear movement.
Herein, a vibration member of a closed loop shape and a self-running type vibration wave driven motor using the same will be described with reference to the accompanying drawings.
FIG. 2 shows an example of a prior-art vibration member 1 having arcuate portions and straight portions and in which a piezo-electric element group 1b is joined to a resilient member 1a having equally spaced-apart grooves 1c.
FIGS. 4A and 4B show an example of a self-running type vibration wave driven motor using the above-described vibration member. The reference numeral 1 designates the vibration member, and the reference numeral 9 denotes a rail-like friction member which is in frictional contact with the vibration member 1. The friction member 9 is brought into pressure contact with the vibration member 1 by a pressing spring 3 with a vibration insulating material 2 (for example, felt) interposed therebetween.
The reference numeral 6 designates a comb-tooth-like movement stopper of which the comb-tooth portion 6a is inserted in a slit in the vibration member 1 in that portion thereof which is not in contact with the friction member 9 on a base stand 8 and supports the vibration member 1 through felt 5 disposed on the bottom of the slit.
The vibration member 1 is supported by a supporting table 4 through the movement stopper 6, the pressing spring 3, etc., and the supporting table 4 in turn is supported by a restraining member 7 for restraining displacement in any other direction than a predetermined direction of movement.
In the above-described example of the prior art, however, only a part of the vibration of the vibration member 1 is used for driving and therefore, efficiency is low and also, the contact between the vibration member and a driven member moved relative thereto is hardly uniform, and this has led to the disadvantage that the drive force is increased and decreased or localized wear occurs, or the necessity of making the surfaces of contact between the vibration member 1 and the driven member parallel and effecting uniform pressing has resulted in disadvantages such as an increased number of parts and an increased adjustment time.
That is, the direction of travel of the travelling wave formed on the resilient member 1 is opposite in the straight portions opposed to each other and therefore, the two straight portions could not be used for rectilinear driving. Thus, only one of the straight portions of the vibration member can be used for driving, and this has led to the above-noted disadvantages.